The present invention relates to a fiber reinforced rubber, particularly, a reinforcement embedded in a rubber.
Since high plessley, high elasticity, high dimensional stability, and high adhesive strength has been required for rubbers such as a belt, a tire, and a hose, a reinforcing cord constructed by fibers or a reinforcing canvas is embedded in a rubber. Generally, a cord of twisted yarns is used for the reinforcement. The yarn may be all twisted, only half of them twisted, or lang lay. The yarns, all of them twisted, are most popular for reinforcement for a rubber.
However, in a rubber reinforced by a twisted yarn, for example, an industrial belt such as a transmission belt and a conveyor belt, maintainability of plessley and maintainability of modulus of elasticity are lowered due to a twisted yarn twisted many times. This shows that maintainability of plessley and maintainability of modulus of elasticity decrease after a certain number of twists.
A rubber reinforced by nontwisted yarn has been known to solve the above problems (maintainability of plessley and maintainability of modulus of elasticity). Although maintainability of plessley and maintainability of modulus of elasticity decrease when the number of twists of a yarn is large, high maintainability of plessley and maintainability of modulus of elasticity can be obtained when the number of twists of a yarn is small, so to speak less twisted. Therefore, a yarn loosely twisted at the optimum maintainability of plessley and maintainability of modulus of elasticity is considered suitable for a rubber.
However, since a rubber reinforced by nontwisted yarn or less twisted yarn possesses disadvantages such as poor dimensional stability and its section is easily deformed to an external stress, destruction of filament is easily caused at a contacting surface to the reinforcement.
A braided cord has been made for various purposes. Since the dimensional stability is especially high due to its structural characteristics in the cylindrically braided cord, more than four and even numbered cords are braided to form a hollow part, the dimensional stability of a rubber is improved and maintainability of plessley and maintainability of modulus of elasticity of a reinforcement are also kept high if a cylindrically braided cord is used for a reinforcement of a rubber.